System Diagnosis - Electronic Ignition

Diagnostic Chart:

CIRCUIT DESCRIPTION
A Crankshaft Position (CKP) sensor determines the engine crankshaft position. The sensor is mounted and protrudes into the rear of the engine block. The sensor is near a slotted wheel on the crankshaft. The rotation of the slotted wheel causes a magnetic flux change in the sensor. This produces a voltage signal from the electronic Ignition Control Module (ICM). The signal creates the reference pulses needed by the Powertrain Control Module (PCM). These signals trigger the correct ignition coil to fire, at the correct time.

The ignition system on this engine uses an individual ignition coil/module for each cylinder. The PCM controls the ignition system operation. There are eight Ignition Control (IC) circuits, one per cylinder, that connect the PCM and the ignition coil/modules. Each ignition coil/module has a power feed, a chassis ground circuit, and a reference low circuit. The PCM causes a spark to occur by grounding the IC circuit, which signals the ignition module to trigger the ignition coil and fire the spark plug. The PCM controls the sequencing and timing. For ignition control circuit schematics, refer to Bank 1 Ignition System or Bank 2 Ignition System.

DIAGNOSTIC AIDS
The following may cause an intermittent:
- Check for poor connections. Check for adequate terminal tension. Refer to Electrical Diagnosis/Repair Procedures for proper procedure.
- Corrosion.
- Mis-routed harness.
- Rubbed through wire insulation.
- Broken wire inside the insulation.

Using Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame and/or Failure Records data can help determine how many miles since the DTC set. The Fail Counter and Pass Counter can also help determine how many ignition cycles the diagnostic reported a pass and/or a fail. Operate vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that you observed. This will isolate when the DTC failed. For an intermittent condition, refer to Symptoms. Testing and Inspection

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
3. Monitoring the misfire current counters determines if a fault is present.
4. A good indication that the fuse is open is all the misfire current counters are incrementing on one side of the engine. Inspect the ignition feed circuit for a grounded circuit.
8. If the fuse is open and no problem can be found with the ignition coil/module circuits, inspect the injector circuits for being grounded. The INJR1 fuse and INJR2 fuse feeds the ignition coil/module circuits and injector circuits.